This invention relates to apparatus and method for controlling tension in a moving web and especially to an improvement in the tension control apparatus of U.S. Pat. No. 4,216,804.
Loom tension control apparatus illustrated in the above patent contemplates the use of an oscillating roll which is carried by the fabric so as to be raised and lowered as tension/speed increases and decreases in the fabric. The oscillating roll is positioned in a horizontal run of the fabric where a change in direction of the fabric occurs. The force exerted by the roll on the fabric may be varied as through the use of a counterweight or a spring so as to adjust the effective weight of the roll and hence the force exerted by gravity against the cloth to provide desirable tension in the fabric being fed to the takeup. Oscillation of the roll carried by the fabric is transmitted through a suitable drive including a chain or the like to a potentiometer or auto- transformer. The continuous oscillations occurring during weaving, produces constant movement and hence wear on all these mechanical parts.
A major problem in the tension control apparatus of devices constructed in accordance with the above patent as well as other similar devices results from wear on the moving parts.
Moreover, adjustment of the various mechanical parts requires manipulation of several components. The range of adjustment for a given movement of the oscillating roll is limited.